Clinical trials have conclusively demonstrated that lowering cholesterol results in large benefits for individuals with coronary heart disease, dramatically reducing the risk of myocardial infarction. While effective pharmacotherapies (i .e., lipid-lowering medications) are available, an estimated minimum of 60% of patients discontinue lipid-lowering medications within one year. Nonadherence to medications is a long- standing, elusive phenomenon that increases utilization and health care costs as well as adversely affecting health outcomes. Existing research demonstrates that a theoretical framework is needed to guide the development and dissemination of effective interventions. Research on the application of the Transtheoretical Model of Behavior Change (TTM) to adherence suggests that the model has strong explanatory power in this area. This Fast-Track research proposal involves the development and clinical trial of TTM based stage-matched, individualized, and interactive interventions for adherence delivered proactively to entire populations of lipid-lowering medication users. Computer based expert system interventions used in conjunction with stage matched self-help manuals have the potential to be more effective than any existing program, offering far greater availability at a low cost. Using the TTM to guide intervention development will provide the theoretical, individualized, and interactive framework that experts in the area have indicated is necessary. PROPOSED COMMERCIAL APPLICATIONS: Nonadherence to lipid-lowering medications is costly to all participants in the health care deliver system. Over 21 million adults with dyslipidemia are eligible for pharmacological intervention. A minimum of 60 % of individuals taking these medications fail to adhere. Nonadherence to lipid-lowering medications increases CHD morbidity and mortality, as well as healthcare utilization. It also costs the pharmaceutical industry over $6 billion in lost revenue. Expert systems that can increase adherence to lipid-lowering medications on a population basis and are cost effective have tremendous commercial potential.